A method to create toner gas gauge by using both pixel count and pixel transition count for different types of image is disclosed. Using the ratio of transition count to pixel count develops an accurate estimation than simple pixel counting of toner consumption based on image types. Due to fringe field development effect, different type of image consumes different toner mass for the same number of pixel counts. By monitoring the transition counts (laser on/off or off/on) a determination can be made as to what type of image is being exposed on a photoreceptor resulting in a better estimation of toner usage.
In a typical electrophotographic printing process, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged photoconductive member is selectively exposed to dissipate the charges thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. The toner particles are attracted to the latent image forming a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. The toner particles are heated to permanently affix the powder image to the copy sheet.
In digital xerographic printers and copiers, the process control software has available the actual number and distribution of pixels in every image. Pixel-counting can and has been used to estimate the amount of toner used in developing a given image. The estimated value representing the amount of toner consumed is used for controlling the addition of toner to the developer housing in a dual component development system, and to indicate the remaining toner left in the EP cartridge in a single component development system.
In a dual component development system, for example, to maintain print quality, toner concentration usually is maintained during machine operation. This may involve adding toner to the developer housing in a controlled fashion during the entire imaging sequence. In a single component development system, toner consumption is usually monitored and a warning signal is given to the user when the condition of xe2x80x9cEnd of Lifexe2x80x9d is nearly approached. In a digital xerographic engine, the number of pixels printed can be roughly correlated to the amount of toner to be used. When using simple pixel counting, the area of pixels developed is taken as fully developed, that is, toner mass developed can be calculated according to the following equation:
Mt=Np*Ap*DMAmax
where:
Mt is the mass of toner developed
Np is the number of pixels developed
Ap is the area of each pixel
DMAmax is the maximum Developed Toner Mass Area which can be developed.
This equation, however, fails to account for the different types of images such as text/line, half tone and solid area printed which will yield different toner mass consumptions, and therefore the estimation generated from this equation may be inaccurate.
A method for estimation of toner usage in digital xerographic process is disclosed. The method calculates a ratio of transition count/pixel count using a pixel transition count and a pixel count for a printed image and provides an estimate of toner consumption based on said ratio of transition count/pixel count.